Question

Fern prothallus is-
A. Homothallic
B. Heterothallic
C. Heterotrophic
D. Heteromorphic

Answer 1

Hint: Ferns are the plants from the class Pteridophyta. They are tracheophyta, i.e., possess vascular tissues that help in conducting water and nutrients. They neither have seeds nor flowers. Ferns reproduce through spores that are released from sporangium. The dominant phase in the life cycle of ferns is the sporophyte which is diploid. Their gametophytes are free-living and have a resemblance to the liverworts.

Complete answer:
The main function of gametophyte is to produce gametes, which after fertilization will form sporophyte generation. Both the sporophyte and gametophyte are free-living in the case of ferns, and thus they show alternation of generation. The fern gametophyte is called prothallus. Prothallus is a green-colored, photosynthetic structure. It does not contain any roots, stems, or leaves but they possess multicellular rhizoids which are the organ for anchoring it to the soil or substratum and helps in absorption. Prothallus has both male and female sex organs, i.e., both antheridia and archegonia on the lower surface of this prothallus and thus it is called homothallic. The prothallus grows in moist, cool, and shady places. The growth of the prothallus is independent for a few weeks, and then further grows to produce sex organs.
Hence, the correct answer is option (A).

Note: Fern prothallus is monoecious. The fern plant is monosporous; it produces a single type of spore. Prothallus germinates from haploid spores and is a small, inconspicuous, and multicellular structure. Prothallus is independent and autotrophic. The prothallus produces sporangia. The sporophyte produces spores through meiosis whereas the gametophyte i.e., prothallus forms gametes by mitosis.